DE 697 297 19 T2 describes an electrical bushing for an active, implantable, medical device—also identified as implantable device or therapy device. Such electrical bushings serve the purpose of establishing an electrical connection between a hermetically sealed interior and an exterior of the therapy device. Known implantable therapy devices are pacemakers or defibrillators, which typically have a hermetically sealed metal housing, which is provided with a connection body, also called header or head part, on one side. The connection body serves for the connection with electrode leads. The connection socket has electrical contacts for electrically connecting the electrode leads to the control electronics in the interior of the housing of the implantable therapy device. On the one hand, provision is thereby made for electrical connections between the connection body and the outer side of the electrical bushing. On the other hand, provision is made for electrical connections between the inner side of the bushing and the control electronics.
The hermetic seal with regard to a surrounding area is a significant prerequisite for an electrical bushing. Conducting elements, which are introduced into an electrically insulating base body and via which the electrical signals proceed, need to thus be introduced into the insulating base body without any gaps. It has proven to be advantageous thereby to embody the conducting elements as cermet. Cermets are composite materials of powdery metal and one or a plurality of ceramics. Cermets make it possible to produce a direct substance-to-substance bond between the conducting element and the surrounding insulating ceramic base body of the bushing by means of co-sintering. If massive metallic conducting wires are used instead of cermets, they need to be introduced into the ceramic in extensive methods in order to establish a hermetically sealed connection. Methods, which require a metallization of the ceramic in the through opening and soldering processing by using solder rings, are used thereby. In particular the metallization in the through opening has proven to be difficult to apply.
On the other hand, cermet composite materials have a limited metal content. In many cases, direct sufficiently stable connections can thus not be established with the help of metal wires between the exposed surfaces of a cermet conducting element and the connection body on the outer side or the control electronics, respectively, on the inner side of a housing. The wires, which are used, often only have a diameter of a few micrometers. Depending on the particle size of the metal or ceramic powder, respectively, which is used, the metal particles in the cermet surface of the exposed area of the conducting element have such a large distance from one another that a reliable direct contacting with a metal wire is not possible in many cases. In such cases, a connection layer, also contact element, which ensures a sufficiently high-tensile connection between the cermet conducting element and a metal wire, is thus required. The contact element is arranged between the conducting element of the electrical bushing and the metal wire. The contact element typically consists of a suitable metal or of a suitable metal alloy.
Such contact elements can be created with known methods, such as printing or PVD methods.
Known printing methods are pad printing and screen printing. If the connection layer is applied via a printing method, a printing paste can be used for example, which includes at least one conducting material. In addition, the paste oftentimes also includes one or a plurality of organic binding agents, such as, for example, an alkyl cellulose. When removing the binding agent by means of heating, a metal layer is obtained, which, on principle, has a strong porosity.
The sputtering, which is known as cathode sputtering process, is a known PVD method. By bombarding with high-energy ions, atoms, which subsequently settle on the substrate, in this case the conducting element, as layer, are knocked out of a solid. Layers created in this way often have a low porosity. The creation of PVD-generated layers with large layer thicknesses is economically unviable.
Printing methods as well as PVD methods are mask-giving methods. If only certain areas of a substrate, here the exposed surfaces of the conducting element, are to be coated with the contact element, a masking of the surrounding areas is required. Masking methods frequently reach their limits at those locations, where very small surfaces or surfaces, which are located closely next to one another, are to be coated. Due to the advancing miniaturization and devices, which become increasingly more complex, this is often associated with problems in the medical technology. Moreover, the printing methods cannot be used to coat curved surfaces. As mentioned above, printing methods often lead to highly-porous connection layers or contact elements, which do not provide for a high-tensile connection with a metal wire. If larger layer thicknesses are required for the contact element, PVD methods are economically not viable. In general, mask-giving methods are not suitable in the case of surfaces to be coated, which are very small and/or which are located closely next to one another.
For these and other reasons, a need exists for the present embodiments.